A fuel cell is a device that generates electrical energy by electrochemical conversion of the chemical energy of fuel instead of burning it into heat. This is an electric generator without a pollution problem and thus has drawn much attention recently.
Fuel cells generate electricity by electrochemically reacting fuel with oxygen; They can supply electric power for various electric/electronic consumer goods, particularly mobile devices as well as for industry, home and vehicles.
Fuel cells may be divided into a solid electrolyte fuel cell, a phosphoric acid fuel cell and a molten carbonate fuel cell depending on the type of electrolyte. Running temperature of fuel cells and materials consisting of the electrolyte may be determined by properties of the electrolyte.
Solid-type PEM fuel cells have been most widely studied as a power source for a vehicle. In PEMFCs, hydrogen and oxygen gases are provided to an oxidation electrode and a reduction electrode, respectively, which generates a current by the following reactions:Oxidation electrode reaction: 2H2→4H++4e−Reduction electrode reaction: O2+4e−+4H+→2H2OTotal reaction: 2H2+O2→2H2O
As shown above, a hydrogen molecule is decomposed, and four hydrogen ions and four electrons are produced in the oxidation electrode. Thus produced electrons move through an outer circuit, thereby generating a current. The hydrogen ions move to the reduction electrode through electrolyte, and participate in the reduction electrode reaction. Obviously, the efficiency of a fuel cell largely depends on the electrode reaction rate.
Electrodes include catalysts. The majority of the electrode catalyst materials are platinum-based metals, which are very expensive and cause the manufacturing cost to increase. It has been reported that the usage of platinum should be lowered to 0.2 g per kW for commercialization of a fuel cell vehicle.
For this purpose, there have been many attempts made to develop non-platinum materials. However, thus developed non-platinum catalyst materials fail to show excellent performance for practical uses, and thus there is still an urgent need for the development of high-performance electrode catalyst materials that can overcome the aforementioned problems.
The information disclosed in this Background Art section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.